JPH08152578A - Manufacture of optical isolator - Google Patents

Abstract

PURPOSE: To provide a method for mass-producing optical isolators with high reliability which enables a large-quantity metallizing process and also enables soldering with high reliability. CONSTITUTION: On the surface of an optical material block 1, grooves 2 which are wider than a cutting margin are formed along cutting expected lines for cutting plural optical elements, a reflection preventive film and a metallized film 3 are formed, and the block is cut along the grooves 2 to manufacture the optical elements 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical isolator using the Faraday effect used in optical communication, optical measurement, etc., and more particularly to a method for manufacturing an optical isolator having excellent environment resistance.

[0002]

2. Description of the Related Art In recent years, an optical communication system using a semiconductor laser as a light source and an optical application device using a semiconductor laser have been widely used.
Has been expanded.

In order to improve the accuracy and stability of these optical communication systems and optical application equipment, an optical isolator is used for the purpose of removing the returning light to the semiconductor laser.

The structure of this optical isolator comprises an optical element consisting of a polarizer, an analyzer and a Faraday rotator, a permanent magnet for generating a magnetic field, and a holder for fixing and protecting them.

Conventionally, organic adhesives have been used as a method of fixing and adhering each optical element and a holder, but the stability of the adhesive force over a long period of time is poor, and in particular the characteristics are affected by environmental changes such as temperature and humidity. Was deteriorating.

Therefore, an optical isolator, such as a repeater for optical communication, which requires a high degree of reliability for a long period of time, is manufactured by a metal fusion method instead of the conventional fixing method using an organic adhesive. Optical isolators have been proposed.

The technique of adhesion and fixing by the metal fusion method is applied to a wide range of applications such as gas turbine blades, vacuum windows of magnetrons and microwave electron tubes, high-power high-frequency propagation transmitter tubes, etc. However, in the optical isolator, the metallization treatment layer for metal fusion fixation is formed on the peripheral portion of the optical element except at least the light transmitting portion, and the holder and the optical element are joined by soldering.

The material used for forming the metallized layer is slightly different depending on the material to be adhered, but in general,
As a base layer, Cr, Ta, W, T for securing adhesion
A layer made of i, Mo, Ni, or Pt, or a layer made of an alloy containing at least one of the above metals is formed, and Au, Ni, Pt, or the like is used as the outermost layer. Further, as an intermediate layer between the underlayer and the outermost layer, N
i, Pt, etc. may be formed.

As the fusion metal, an Au--Sn alloy,
Solder materials such as Pb-Sn alloys and Au-Ge alloys and various brazing materials are used, but Au-Sn alloy solders that have a high adhesion strength and a relatively low fusion temperature are in terms of adhesion strength and workability. Since it is excellent, it is desirable as a material for metal fusion fixing.

As the method for forming the metallized layer described above, a wet process by a plating method and a vacuum deposition method,
Dry processes such as sputtering are known, but scratches occur on the optical surface of the optical element or the antireflection film,
In addition, a dry process is often used to prevent the adhesion of dust.

[0011]

However, when the metallized film is formed by the vacuum evaporation method or the sputtering method, there is a serious problem in mass productivity.

That is, according to the conventional metallizing method, after forming an antireflection film on the surface of the optical material block, it is cut into a size corresponding to one optical element, and as shown in FIG. Of the light-transmitting portion of the mask is masked and the optical element 5 and the metal mask 7 are fixed by the substrate holder 6 and the jig 8 so that the metallized film is formed only on the unmasked portion. The metallized film was produced by a dry process.

At this time, since the optical elements are washed and set on the jig one by one, a great number of man-hours are required, and it is difficult to metalize a large number of optical elements.

Therefore, in order to improve mass productivity, after forming an antireflection film (not shown) on the optical material block 1 having a size capable of cutting out several tens of optical elements 5 as shown in FIG. When the metallized film 3 was formed and then cut along the line shown by the dotted line in the figure (only one optical element is shown in the figure), the bonded portion peeled off after cutting or after solder bonding. However, many of them did not have sufficient adhesive strength, yield was poor, and improvement in mass productivity could not be achieved.

[0015]

According to the present invention, a groove is formed in advance along a planned cutting line of an optical material block having a size capable of cutting out a plurality of optical elements, and then an antireflection film is formed. Also, by forming a metallized film for metal fusion bonding between the optical element and the holder and cutting the metallized film with a narrower cutting width than the groove, a large number of metallized optical elements can be obtained in a simple process. A high-performance optical isolator with excellent environmental resistance can be obtained.

[0016]

[Function] A metallized film is formed on the surface of a large optical material block in an area for a plurality of optical elements, cut into individual optical element sizes, and the metallized film is peeled off from the soldered and adhered sample. When the fracture surface of the peeled portion was observed in detail, as shown in FIG. 4, the peeled portion 15 was indicated not by the metallized film 3 but by the reference numeral 1 directly below the metallized film.
It was found that this occurs from inside the optical element shown by 4.

That is, it is considered that the cause of the peeling is that strong stress is generated in the optical element due to heat generated between the cutting blade and the optical element through the metallized film at the time of cutting and mechanical impact. To be

Therefore, when the optical element is cut after the metallized film is formed, the cut portion may be separated from the metallized film so that heat and mechanical shock at the time of cutting do not affect the optical element.

From the above conclusion, as shown in FIG. 1 (a), the optical material block 1 is preliminarily provided with the groove 2 along the cut portion.
Is formed, and thereafter, as shown in FIG.
An antireflection film (not shown) and a metallized film 3 are formed. Further, thereafter, as shown in FIG. 1C, a blade having a cutting width 4 smaller than the groove width of the groove 2 is used to cut the metallized film 3 so that the blade and the metallized film 3 do not come into contact with each other (2 The shaded area surrounded by the dots of the book).

By the steps described above, the stress generated in the optical element directly under the metallized film can be suppressed to a minimum, and the optical element will not be peeled off even after solder bonding.

[0021]

EXAMPLES The present invention will be described below by way of examples in comparison with comparative examples (prior art).

As shown schematically in FIG. 1, the dimension is 1
Eight rut grooves 2 each having a width of 330 μm and a depth of 350 μm are formed in a grid pattern of four at a pitch of 1.82 mm on a rutile single crystal (optical material block) 1 of 1.0 × 11.0 × 1.0 (mm). Then, grooving for taking 25 optical elements was performed [however, 9 optical elements are shown in FIGS. 1 (a) and 1 (b)]. Next, the antireflection film and the metallized film 3 were formed. After that, the cutting width 4 is 200 μm
The blade was cut at the center of the groove to produce an optical element 5 having a 1.6 mm opening with 25 metallized films.

[0023]

Comparative Example In the example, the antireflection film and the metallized film were formed without forming the grid-like grooves, and the cutting width was 200 μm.
The blade was cut with a blade of m to prepare an optical element having 25 openings of 1.6 mm.

The metallized film-coated optical elements of the examples and comparative examples were soldered to a gold-plated stainless steel holder, and then an adhesion test was performed between the optical element and the holder. I got the result. In addition,
As shown in FIG. 5, the test method of the adhesion test is as follows. The holder 9 is fixed to the support base 12, a load is applied to the optical element 5, and the load at the time of peeling is read by the push-pull gauge 13.
Adhesion.

[0025]

[Table 1]

As can be seen from Table 1, the examples of the present invention have high adhesion and are all good products of 1 kg or more.

In the embodiment, the blade for grooving and the blade for cutting are prepared separately, but the same grooving and cutting can be performed using the same blade. That is, in grooving, the blade may be passed a plurality of times with a pitch shifted with respect to one groove, and in cutting, the flade may be passed once.

Further, in the embodiment of the present invention, FIG.
Although the cross-sectional shape of the groove 2 is rectangular as shown in FIG. 2, it is sufficient if it is not directly subjected to thermal / mechanical impact by the blade and the optical material block at the time of cutting. Alternatively, it may be oval.

Further, when the metallized film is formed on both surfaces of the optical material block, the groove may be formed on both surfaces in advance, and the present invention is not limited to the embodiment.

[0030]

As described above, according to the present invention,
By forming the groove in the optical element in advance, a large amount of metallization processing can be performed, highly reliable solder bonding can be performed, and a highly reliable optical isolator can be mass-produced.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a schematic process of an embodiment of the present invention. FIG.
1A is a diagram showing a state where a groove is formed in an optical material block, FIG. 1B is a diagram showing a state where a metallized film is formed, and FIG. 1C is a diagram showing a cutting state, Figure 1 (d)
[FIG. 3] is a cross-sectional view of individual optical elements after cutting.

FIG. 2 is an explanatory diagram showing an outline of a conventional metallizing method. 2A is a perspective view and FIG. 2B is a sectional view.

FIG. 3 is an explanatory view showing an outline of a conventional optical element manufacturing method.

FIG. 4 is an explanatory view schematically showing a peeled state after solder bonding.
4A is a sectional view, and FIG. 4B is a plan view.

FIG. 5 is an explanatory diagram showing an outline of a solder joint adhesion strength test method.

[Explanation of symbols]

 1 Optical Material Block 2 Grooves 3 Metallized Film 4 Cutting Width 5 Optical Element 6 Substrate Holder 7 Metal Mask 8 (Mask Holding) Jig 9 Holder 10 Solder Layer 12 Supporting Stand 13 Push-Pull Gauge 14 Optical Element Breaking Point 15 Peeling Part

Claims (1)

[Claims] 1. A groove is formed in advance on a surface of an optical material block having a size capable of cutting out a plurality of optical elements along a planned cutting line, and then an antireflection film and a metal fusion bonding with a holder. A method of manufacturing an optical isolator, which comprises forming a metallized film for forming a groove and cutting the groove with a cutting width narrower than the groove width of the groove.